The invention relates to instrumentation and techniques for ophthalmic surgery, particularly although not necessarily as the same pertains to cataract surgery.
Surgically induced astigmatism and inflammation limit the rate and the extent of visual rehabilitation following cataract surgery. To reduce the extent of these surgically induced limitations on visual rehabilitation, a number of new advances in surgical techniques have been developed. In particular, the advent of phacoemulsification in combination with long scleral-tunnel incisions has greatly reduced surgically induced astigmatism and inflammation, in addition to reducing the post-operative time necessary for the restoration of vision. Illustration and discussion of such techniques will be found in the book, "Small-Incision Cataract Surgery", edited by Drs. James P. Gills and Donald R. Sanders, published 1990 by SLACK Incorporated, Thorofare, New Jersey.
Despite these advances in technique, the performance of cataract surgery through a scleral-tunnel incision is technically difficult and may result in serious complications. One of the greatest difficulties is that of advancing instruments, such as surgical knives or intraocular lenses, through the scleral-tunnel incision without getting them caught on a part of the scleral tunnel. Inadvertent capture of a knife in the sclera can result in serious complications, such as the formation of false passageways, hemorrhage, or penetration into the retina and vitreous cavity.
Another dificulty arises from corneal folds and/or deformation of the eye, as can be induced by a straight instrument advanced through a scleral-tunnel incision. Typically, this difficulty results from incompatability of a straight instrument with the native curve of a scleral tunnel, and the need to angularly manipulate the instrument, from a direction which faces the cornea upon exit from the incision, to a direction which faces the cataractous lens. The combined effect of these factors interferes with the surgeon's visualization of the cataract during its removal, and can lead to complications such as corneal-endothelial injury, disruption of the posterior-lens capsule, and increased vitreous pressure.